I am a long-time fan of Hermida, so I'm inclined to say this deal favors the Red Sox. Hermida was a shining star as he rose through the Marlins farm system, but is yet to blossom as a major-leaguer. Still just 25 years old, it's reasonable to think that Hermida still has some developing to do. Perhaps all his nagging injuries have stunted his growth as well.
In Jeremy Hermida, Boston got a sweet left-handed swing that I think has some power we are yet to see. Jeremy also has a good eye for the strike zone, but a better understanding of pitches he can't square up is the next step for him. Either that, or closing the holes in his swing. Still, Boston now has a legitimate replacement for Jason Bay, should he leave. Frankly, Hermida's defense is better, and he is younger and cheaper. Bay is a bad contract waiting to happen, and now Boston shouldn't feel so much pressure to cave in.
Hunter Jones, although only 25 years old, pretty much is what he is. He is somewhere between a AAA and AAAA bullpen lefty. It is nice to have southpaws, but he won't challenge guys like Dan Meyer and Renyel Pinto in the Marlins bullpen.
The real catch in this deal for Florida is Jose Alvarez. He is a bit undersized, but a left-hander who came on strong the second half of this year. He is only 20 years old, and is still at least a few years away from the majors. Looking at his numbers, I am not all that high on him. His ERA dropped thanks to a home run rate that plummeted. Alvarez doesn't miss too many bats, and while he is still quite raw, great pitchers tend to miss minor league bats more than Alvarez has (especially with his fly ball rate).
Theo Epstein says that the Red Sox bought low on Jeremy Hermida, and I'd agree with him. Frankly, the Tigers gave up a better package (Luke French and Mauricio Robles) for two months of Jarrod Washburn than Boston gave up for a couple years of Jeremy Hermida. I wouldn't trade Washburn for Hermida straight up, especially when their age and contracts are considered.
Florida must see something in Alvarez, and their scouting department gets it right pretty often. Still, even if Alvarez develops and Hermida does not develop any further, I think this is a nice deal for Boston.